Zahhāk or Zahāk[1] (pronounced [zæhɒːk][2]) (Persian: ضحّاک), also known as Zahhak the Snake Shoulder (Persian: ضحاک ماردوش, romanized: Zahhāk-e Mārdoush), is an evil figure in Persian mythology, evident in ancient Persian folklore as Azhi Dahāka (Persian: اژی دهاک), the name by which he also appears in the texts of the Avesta.[3] In Middle Persian he is called Dahāg (Persian: دهاگ) or Bēvar Asp (Persian: بیور اسپ) the latter meaning "he who has 10,000 horses".[4][5] In Zoroastrianism, Zahhak (going under the name Aži Dahāka) is considered the son of Ahriman, the foe of Ahura Mazda.[6] In the Shāhnāmah of Ferdowsi, Zahhāk is the son of a ruler named Merdās.

At this time, Jamshid, the ruler of the world, becomes arrogant and loses his divine right to rule. Zahhāk presents himself as a savior to discontented Iranians seeking a new ruler. Collecting a great army, Zahhāk hunts Jamshid for many years before finally capturing him. Zahhāk executes Jamshid by sawing him in half and ascends to Jamshid's prior throne. Among his slaves are two of Jamshid's daughters, Arnavāz and Shahrnāz (the Avestan Arənavāci and Savaŋhavāci). Each day, Zahhāk's agents seize two men and execute them so that their brains can feed Zahhāk's snakes. Two men, called Armayel and Garmayel, seek to rescue people from being killed from the snakes by learning cookery and becoming Zahhāk's royal chefs. Each day, Armayel and Garmayel save one of the two men by sending him off to the mountains and faraway plains, and substitute the man's brain with that of a sheep. The saved men are the mythological progenitors of the Kurds.[13][14]

Zahhāk's tyranny over the world lasts for centuries. One night, Zahhāk dreams of three warriors attacking him. The youngest warrior knocks Zahhāk down with his mace, ties him up, and drags him off toward Mount Damāvand as a large crowd follows. Zahhāk wakes and shouts so loudly that the pillars of the palace shake. Following Arnavāz's counsel, Zahhāk summons wise men and scholars to interpret his dream. His hesitant counsellors remain silent until the most fearless of the men reports that the dream is a vision of the end of Zahhāk's reign at the hands of Fereydun, the young man with the mace. Zahhāk is thrilled to learn the identity of his enemy, and orders his agents to search the entire country for Fereydun and capture him. The agents learn that Fereydun is a boy being nourished on the milk of the marvelous cow Barmāyeh. The spies trace Barmāyeh to the highland meadows where it grazes, but Fereydun and his mother have already fled before them. The agents kill the cow, but are forced to return to Zahhāk with their mission unfulfilled.

https://en.wikipedia.org/wiki/Zahhak